This thesis explores new and existing cellulose nanocrystal (CNC) production methods and evaluates their effects on CNC properties, with emphasis on their thermal performance. CNCs produced from industrial and lab-scale processes possess a wide range of surface chemistries, surface charge contents, as well as structural and morphological properties which affect their performance in CNC-based applications. Despite the broad range of available CNC properties, some challenges persist, particularly in the incorporation of CNCs into hydrophobic matrices, high brine liquid formulations, and high temperature applications. Herein, sulfated and carboxylated CNCs produced from large-scale processes were thoroughly characterized and key differences in their thermal performance and self-assembly and rheological behaviors were identified. Furthermore, an optimization study on phosphoric acid hydrolysis parameters and a novel surface modification method which deposits cellulose phosphate oligosaccharides onto CNC surfaces were proposed. The optimization study revealed that CNCs with high colloidal stability could not be produced with phosphoric acid alone; however, the weak acid hydrolysis allowed for precise control over CNC length. The deposition of oligosaccharides onto CNCs, however, resulted in highly colloidally stable CNCs possessing both phosphate and sulfate functional groups. Furthermore, this surface modification method altered CNC surface charge content, water interactions, and the viscosity of their aqueous suspensions. In these studies, however, changes in CNC thermal performance were difficult to elucidate. As such, to further understand the effects of CNC properties on both their dried and aqueous form thermal performance, a systematic comparison of sulfated, phosphated, and carboxylated CNCs was performed. CNCs were produced with new acid blend hydrolyses (i.e., combining sulfuric and phosphoric acid) as well as existing organic acid hydrolyses and oxidation routes. The combined effects of surface chemistry and counterion profoundly affected the thermal performance of dried CNCs, whereby sulfated and carboxylated CNCs were less thermally stable with proton and sodium counterions, respectively. Additionally, dried CNCs with more surface charge groups, shorter cellulose chains, and higher specific surface areas were found to be less resistant to high temperatures. As such, the new CNCs produced with acid blends exhibited superior thermal performance in their dried form due to their lower charge contents and longer cellulose chains. In their aqueous suspension form, carboxylated CNCs far outperformed both sulfated and phosphated CNCs at high temperatures; their suspensions remained colloidally stable at temperatures up to 150°C for extended time periods. Overall, this thesis equips CNC users and researchers with knowledge and tools to expand the usage of CNCs in commercial applications, particularly those which require high temperatures such as melt-processed polymer composites and oil and gas extraction fluids. / Thesis / Doctor of Philosophy (PhD) / This thesis contributes to a broader effort in replacing non-renewable and emissions intensive materials with sustainable alternatives such as nanocellulose. Nanocelluloses are nanometer-sized (where one nanometer is one billionth of a meter) cellulose particles manufactured from wood, cotton, or other natural resources. Nanocelluloses are made within Canada on a tonne-per-day scale; this value-added wood product presents an opportunity to refresh the Canadian forest industry. While nanocelluloses have many potential applications, their usage is somewhat limited by their inability to resist heat. This thesis examines changes in nanocellulose properties at high temperatures and evaluates how nanocellulose production methods affect their particle properties and thermal performance. New production methods are explored that increase nanocellulose resistance to heat, alter their dimensions, and change their interactions with water. Overall, this work aims to expand the usage of nanocellulose in commercial products such as coatings, plastics, industrial fluids, food products, and cosmetics (to name a few) by helping researchers select the right kind of nanocellulose for their intended applications.

Understanding and controlling the forces between colloidal particles in solution, along with the resulting stability of a dispersion of such particles, continues to be at topic of great interest. Although most laboratory studies focus on model systems in which the number of system species is kept to a minimum, real colloidal systems can be much more complex, consisting of multiple components that can vary greatly in size, charge, shape, etc. This dissertation focused on a topic that has received very little prior study, namely synergistic effects that can arise in mixed colloidal systems in which the resulting force and stability of the system cannot be predicted using results obtained in more idealized systems consisting of fewer components. Two specific systems were studied. The first was a ternary system of particles in which micron-sized particles were in a dispersion containing both nanoparticles and submicron particles. It was shown through both computation modeling and direct force measurements that the nanoparticles can create attractive forces between the micron and submicron particles such that a halo of submicron particles is formed. This halo results in long range forces between the microparticles that cannot be predicted from measurements in systems containing only nanoparticles or only submicron particles. In addition, the forces can be large enough to alter the stability of a dispersion of these microparticles. The second system consisted of microparticles in a solution containing nanoparticles and a polyelectrolyte, specifically poly(acrylic) acid. Again, through modeling and experimentation, it was found that complexation of the nanoparticles and polyelectrolyte molecules led to depletion and structural forces between the microparticles that were substantially greater than the sum of the forces measured in systems of only nanoparticles or only polyelectrolyte. It was also found that these greater forces could lead to destabilization of a dispersion of microparticles that was stable when only nanoparticles or only polyelectrolyte was present. While these results clearly demonstrate the difficulty associated with predicting forces and stability in mixed colloidal systems, they also indicate that such systems offer new and interesting opportunities for controlling stability that clearly warrant additional study. / Ph. D.

This dissertation focused on the potential use of highly charged nanoparticles to stabilize dispersions of weakly charged microparticles. The experimental components of the project centered on a model colloidal system containing silica microparticles at the isoelectric point where the suspensions are unstable and prone to flocculation. The stability of the silica suspensions was studied in the presence of highly charged nanoparticles. Initial experiments used polystyrene latex with either sulfate or amidine surface groups. Effective zeta potentials were measured with nanoparticle concentrations ranging from 0.001% to 0.5% vol. Adsorption levels were determined through direct SEM imaging of the silica microparticles, showing that the nanoparticles directly adsorbed to the microparticles (amidine more than sulfate), producing relatively large effective zeta potentials. However, stability experiments showed that the latex nanoparticles did not stabilize the silica but merely provided a reduction in overall flocculation rate. It was concluded that the zeta potential was an insufficient predictor of stability as there was still sufficient patchiness on the surface to allow for the silica surfaces to aggregate. Experiments using zirconia and alumina nanoparticles did achieve effective stabilization; both types stabilized the silica suspensions for longer than the observation period of approximately 15 hours. Stability was observed at concentrations of 10^-4% to 1.0% (zirconia) and 10^-2% vol. (alumina). These particles adsorbed directly to the microparticles (confirmed via SEM) and produced increasing effective zeta potentials with increasing nanoparticle concentrations. The adsorption resulted in significant electrostatic repulsion that was determined to be effectively irreversible using colloidal probe AFM. The improved stabilizing ability was attributed to the increased van der Waals attraction between the oxide nanoparticles (compared to polystyrene). Finally, an unexpected result of the CP-AFM force measurements showed that the repulsive forces between a nanoparticle-coated particle and plate lacked the normal dependence on the radius of the probe as predicted by the Derjaguin approximation. The forces observed in nanoparticle suspensions were virtually identical for 5 µm and 30 µm probes. Based on calculations of the shear rate in the gap, it was theorized that this phenomenon may have resulted from the shearing of adsorbed particles from the surfaces, which leads to similar interaction geometries for the two probe sizes. / Ph. D.

A utilização de nanopartículas magnéticas em biomedicina e biotecnologia vem recebendo elevado destaque nos últimos anos, graças à versatilidade de aplicações como reparo de tecidos, diagnósticos, ressonância magnética por imagem, tratamento contra o câncer, separação celular, transporte controlado de drogas, entre outras. Atualmente, as nanopartículas com potencialidade de aplicação em biomedicina se restringem aos óxidos magnéticos de ferro, os quais apresentam comportamento superparamagnético a temperatura ambiente e magnetização da ordem de 300 emu/cm3. Entretanto, há necessidade inerente da funcionalização da superfície para possibilitar aplicações biomédicas tornando as nanopartículas biocompatíveis e/ou biosseletivas. Essa funcionalização adicional é obtida geralmente introduzindo camadas de materiais diamagnético e/ou paramagnéticos na superfície das NP, as quais baixam a eficiência das propriedades magnéticas exigindo o desenvolvimento de núcleos com elevado valor de magnetização de saturação. Desta forma, nesse trabalho foram sintetizadas nanopartículas magnéticas metálicas de FePt recobertas com óxido de ferro obtidas via processo poliol modificado combinado com a metodologia de crescimento mediado por sementes. Os núcleos magnéticos como-sintetizados foram recobertos com uma camada de sílica, seguido pelo recozimento em atmosfera redutora para elevar o valor da magnetização de saturação. Em seguida, sobre a superfície de sílica foram ancoradas moléculas luminescentes de rodamina B com o auxílio de moléculas de APTES atuando como grupo sililante e as NP resultantes foram novamente recobertas com uma fina camada de sílica. Os resultados permitem concluir que foi obtido um sistema bifuncional combinando em uma única nanopartícula a possibilidade de sensoriamento óptico e magnético, além de possuir sua magnetização de saturação intensificada cerca de 10 vezes em relação aos óxidos metálicos (64 emu/g), manter o caráter superparamagnético e possuir superfície biocompatível com possibilidades de funcionalizações adicionais, com grande potencial para aplicações em biomedicina. / In recent years, the magnetic nanoparticles uses in many biomedical and biotechnological areas have received great attention due to their several applications possibilities such as: tissue repair, diagnostics, magnetic resonance imaging, cancer treatment, cell separation, and controlled drug delivery, among others. Today, the potential magnetic nanoparticles applications are limited to magnetic iron oxides uses, which exhibit superparamagnetic behavior at room temperature and low saturation magnetization around 300 emu/cm3. However, for biomedical applications, the nanoparticle surface must be properly functionalized in order to confer biocompatibility and biosselectivity. These additional functionalizations are generally obtained by paramagnetic and/or diamagnetic materials incorporations onto the nanoparticle surface leading a dramatic decreasing in the already low saturation magnetization. In this context, the development of new magnetic nuclei with high magnetizations values is required. Thus, in this work iron oxide-coated metallic FePt magnetic nanoparticles were synthesized by using the modified polyol process combined with the seed mediated growth method. The magnetic as-synthesized nuclei were coated with a thin silica shell followed by thermal annealing under reducing atmosphere in order to increase the saturations magnetization of this material. After that, onto the silica-coated magnetic nanoparticles surface luminescent dye Rhodamine B molecules were supported using the APTES as intermediate sililant molecules. Then, the functionalized nanoparticles were coated again with an outer layer. In conclusion, according to the obtained results, a bifunctional system combining the optical and magnetic sensing in the same nanoparticle was reported. The obtained nanoparticles present superparamagnetic behavior and high saturation magnetization around 10 times higher (~64 emu/g) compared with the iron oxide nanoparticles synthesized at the same conditions. In addition, the luminomagnetic nanoparticle surface is biocompatible allowing additional future functionalizations with high potential to biomedical applications.

Per via degli svantaggi inerenti l’uso di bentonite nella produzione di vini bianchi, la ricerca di alternative ha assunto di recente una grande importanza. Il lavoro presentato in questa tesi ha l’obiettivo di valutare l’applicabilità di tre approcci innovativi alla stabilizzazione colloidale dei vini: l’uso di chitosano, l’applicazione dei PEF e il riutilizzo di colonne di scambio cationico. L’aggiunta di chitosano è risultata nella rimozione delle chitinasi dal vino, permettendo di raggiungere un soddisfacente livello di stabilità. Gli effetti sul colore e sugli aromi, quando non significativi, non sono risultati essere peggiori rispetto ai risultati ottenuti da trattamenti con bentonite. L’applicazione dei PEF aveva lo scopo di innescare la denaturazione e l’aggregazione delle proteine tramite un sistema di trattamento-raffreddamento e filtrazione finale. I risultati suggeriscono che un buon grado di stabilità viene raggiunto solo con trattamenti particolarmente energetici ma questo a danno del colore del prodotto. Infine, lo scopo dello studio sulle resine di scambio cationico era quello di valutare la rigenerazione di questo supporto per un molteplice utilizzo operativo. La rimozione delle proteine adsorbite sul supporto è risultata essere possibile in specifiche condizioni di pH e forza ionica, con un consumo di acqua relativamente basso. / The search for fining alternatives to bentonite has assumed great importance in white winemaking due to the drawbacks of bentonite application. The research here presented aimed at observing the viability of three innovative approaches to wine stabilization, namely chitosan addition, PEF treatments and cation exchange applicability. Chitosan successfully removed chitinases from wine, allowing at the same time a sufficient degree of colloidal stability. Collateral effects on color and aroma compounds were non-significant or acceptable when compared with the effects observed for bentonite applications reported in literature. The use of PEF was aimed at accelerating protein unfolding and aggregation and was coupled to an in-line cooling and filtration system for efficient removal of colloidal aggregates. The results collected suggested that the treatment was capable of inducing a satisfactory colloidal stability only in high- energetic double-treated wine samples, with some deleterious consequences on the color. Finally, the aim of the research for cation-exchange resins application was to find environmentally friendly cleaning procedures to regenerate the resin capacity and allow reuse of the same resin for further cycles of fining. The removal of proteins bound to the resin was possible under specific pH and ionic strength conditions with relatively low consumption of water.

A utilização de nanopartículas magnéticas em biomedicina e biotecnologia vem recebendo elevado destaque nos últimos anos, graças à versatilidade de aplicações como reparo de tecidos, diagnósticos, ressonância magnética por imagem, tratamento contra o câncer, separação celular, transporte controlado de drogas, entre outras. Atualmente, as nanopartículas com potencialidade de aplicação em biomedicina se restringem aos óxidos magnéticos de ferro, os quais apresentam comportamento superparamagnético a temperatura ambiente e magnetização da ordem de 300 emu/cm3. Entretanto, há necessidade inerente da funcionalização da superfície para possibilitar aplicações biomédicas tornando as nanopartículas biocompatíveis e/ou biosseletivas. Essa funcionalização adicional é obtida geralmente introduzindo camadas de materiais diamagnético e/ou paramagnéticos na superfície das NP, as quais baixam a eficiência das propriedades magnéticas exigindo o desenvolvimento de núcleos com elevado valor de magnetização de saturação. Desta forma, nesse trabalho foram sintetizadas nanopartículas magnéticas metálicas de FePt recobertas com óxido de ferro obtidas via processo poliol modificado combinado com a metodologia de crescimento mediado por sementes. Os núcleos magnéticos como-sintetizados foram recobertos com uma camada de sílica, seguido pelo recozimento em atmosfera redutora para elevar o valor da magnetização de saturação. Em seguida, sobre a superfície de sílica foram ancoradas moléculas luminescentes de rodamina B com o auxílio de moléculas de APTES atuando como grupo sililante e as NP resultantes foram novamente recobertas com uma fina camada de sílica. Os resultados permitem concluir que foi obtido um sistema bifuncional combinando em uma única nanopartícula a possibilidade de sensoriamento óptico e magnético, além de possuir sua magnetização de saturação intensificada cerca de 10 vezes em relação aos óxidos metálicos (64 emu/g), manter o caráter superparamagnético e possuir superfície biocompatível com possibilidades de funcionalizações adicionais, com grande potencial para aplicações em biomedicina. / In recent years, the magnetic nanoparticles uses in many biomedical and biotechnological areas have received great attention due to their several applications possibilities such as: tissue repair, diagnostics, magnetic resonance imaging, cancer treatment, cell separation, and controlled drug delivery, among others. Today, the potential magnetic nanoparticles applications are limited to magnetic iron oxides uses, which exhibit superparamagnetic behavior at room temperature and low saturation magnetization around 300 emu/cm3. However, for biomedical applications, the nanoparticle surface must be properly functionalized in order to confer biocompatibility and biosselectivity. These additional functionalizations are generally obtained by paramagnetic and/or diamagnetic materials incorporations onto the nanoparticle surface leading a dramatic decreasing in the already low saturation magnetization. In this context, the development of new magnetic nuclei with high magnetizations values is required. Thus, in this work iron oxide-coated metallic FePt magnetic nanoparticles were synthesized by using the modified polyol process combined with the seed mediated growth method. The magnetic as-synthesized nuclei were coated with a thin silica shell followed by thermal annealing under reducing atmosphere in order to increase the saturations magnetization of this material. After that, onto the silica-coated magnetic nanoparticles surface luminescent dye Rhodamine B molecules were supported using the APTES as intermediate sililant molecules. Then, the functionalized nanoparticles were coated again with an outer layer. In conclusion, according to the obtained results, a bifunctional system combining the optical and magnetic sensing in the same nanoparticle was reported. The obtained nanoparticles present superparamagnetic behavior and high saturation magnetization around 10 times higher (~64 emu/g) compared with the iron oxide nanoparticles synthesized at the same conditions. In addition, the luminomagnetic nanoparticle surface is biocompatible allowing additional future functionalizations with high potential to biomedical applications.

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1-Microevaporation - Microfluidics is the branch of fluid mechanics dedicated to the study of flows in the channel withdimensions between 1 micron and 100 micron. The object of this chapter is to illustrate the basicprinciples and possible applications of microfluidic chip, called microevaporator. In the first part ofthe chapter, we present a detailed description of the physics of microevaporators using analyticalarguments, and describe some applications. In the second part of the chapter, we present theexperimental protocol of engineering of micro evaporator and different type of microfluidics device.2- On-chip microspectroscopy - The object of this chapter is to illustrate a method to measure absorption spectra during theprocess of growth of our materials in our microfluidic tools. The aim is to make an opticalcharacterization of our micro materials and to carry-out a spatio-temporal study of kineticproperties of our dispersion under study. This instrumental chapter presents the theoretical basis !of the method we used.3-Role of colloidal stability in the growth of micromaterials - We used combined microspectroscopy and videomicroscopy to follow the nucleation and growth ofmaterials made of core-shell Ag@SiO2 NPs in micro evaporators.!We evidence that the growth is actually not always possible, and instead precipitation may occurduring the concentration process. This event is governed by the concentration of dispersion in thereservoir and we assume that its origin come from ionic species that are concentrated all togetherwith the NPs and may alter the colloidal stability en route towards high concentration. 4-Microfluidic-induced growth and shape-up of three-dimensional extended arrays of denselypacked nano particles - In this chapter I present in details microfluidic evaporation experiments to engineer various denselypacked 3D arrays of NPs.5-Bulk metamaterials assembled by microfluidic evaporation - In this chapter I introduced the technique we used (microspot ellipsometry) in close collaborationswith V.Kravets and A.Grigorenko(University of Manchester) and with A.Aradian, P.Barois, A.Baron,K.Ehrhardt(CRPP, Pessac) to characterized the solids made of densely packed NPs. I describe theconstraints that emerge from the coupling between the small size of our materials and the opticalrequirements, the analysis and interpretation of the ellipsometry experiments show that for thematerial with high volume fraction of metal exists the strong electrical coupling between the NPsand the materials display an extremely high refraction index in the near infra-red regime.